Need another reason to avoid fast food? According to new research from the University of Toronto, the grease-proof paper wrappings used for fast food and microwave popcorn may also allow perfluoroalkyls — synthetic chemicals that repel oil, grease and water — to migrate from the wraps into your food. When you eat the food, these chemicals are released into your blood stream. PFOA and PFOS are the two most common perfluoroalkyl chemicals and are known contaminates in human blood worldwide.

What’s so bad about PFOAs?

Studies show that PFOAs and other perfluoroalkyls can cause changes in sex hormones and cholesterol. During studies of PFOAs, rats and mice who have been exposed to PFOAs have experienced both early death and delayed development and some rats even developed tumors due to long-term PFOA exposure. Because rats aren’t humans, scientists can’t say for sure if tumors may occur in humans as well, but still, it’s not good news if you’re feeding your family fast food. Even more unsettling, PFOAs have also been found in umbilical cord blood samples of newborn babies, showing that exposure even starts before birth.